Abstract Recent investigations aimed at estimating the distance to the young
LMC cluster NGC 1866 have made use of Red Clump stars in the
surrounding LMC field, together with empirical and theoretical
Main-Sequence fitting methods, and have found significantly different
distances for the field and the cluster, the latter being closer by in
distance modulus by
(
DM) ~ 0.20 mag. In this paper we
(re-)consider the Cepheid star population of NGC 1866, to try to shed
some light on this discrepancy. By combining various extensive
photometric datasets in
B,
V, I and single-epoch 2MASSJHK
photometry,
PL relationships for the cluster Cepheids are obtained.
A comparison between the field LMC and cluster
PL relationships for
the reddening free Wesenheit index gives a firm determination of the
distance between the cluster and the LMC main body (0.04 mag in
distance modulus, the cluster being more distant) which, coupled to a
model for the geometry of the LMC disk, provides
(
DM) ranging
between 0.0 and -0.11 mag. The simultaneous comparison of the
PL
relationships in
B,
V and
I for the cluster and LMC field gives
an estimate of the cluster reddening, which results to be
E(B-V) =
0.12
0.02. This determination is higher than the canonical
value of 0.06 mag used in all previous studies, but we show that it is
not in contradiction with a re-analysis of independent estimates. The
adoption of the LMC extinction law recently presented by Gordon et al.
(2003) does not change these results. The cluster Main Sequence
fitting distance obtained with this new reddening is
DM = 18.58
0.08, fully compatible with the Red Clump value of
DM = 18.53
and the Cepheid constraint
on
(
DM). Finally, we determined the distance to the cluster
by using a Cepheid Wesenheit
PL relationship with slope coming from
LMC observations, and absolute magnitude zero point calibrated on
Hipparcos parallaxes of Galactic Cepheids, in the assumption that
the relationship is independent of metallicity; the resulting
DM =
18.65
0.10 is not an accurate estimate of the LMC distance
because of possible metallicity effects but, when compared to the
revised Main Sequence fitting value, it points out to a possibly weak
dependence of the Wesenheit
PL relationship on the Cepheid chemical
composition, at least in the period range between 2.5 and 3.5 days.